Calk assembly



Aug. 14, 1956 J. EDWARDES CALK ASSEMBLY Filed Jan. 28, 1954 INVENTUR. Jain .Zd'Wa/aa Y/fm CALK ASSEMBLY John Edwardes, Utica, Mich. Application January 28, 1954, Serial No. 466,644 6 Claims. (Cl. 36-59) This invention relates to new and useful improvements in a nonslip insert or calk primarily adapted and preeminently suited for use on rubber-soled footgear such as fishing Waders and the like.

Rubber-soled footgear such as fishing waders, plimsolls, seamens storm boots, knee boots, rubber-soled leather hunting boots and the like often are unsafe in wet weath r, as water is a natural lubricant for rubber. Yet, footwear of this type frequently is used on fishing, hunting, and camping trips where the wearer frequently is exposed to dangerous situations. Fishermen, for example, frequently wade about in streams on slippery moss-covered rocks. Under these conditions a slip may mean a wetting for the wearer or even result in a bad accident.

An important object of the present invention is to .provide a calk assembly that is particularly adapted for use on rubber-soled footgear such as that referred to specifically above and that assures an efiicient gripping action on substantially any natural surface.

Another object of the invention is to provide a calk of the above-mentioned character that can be readily replaced when worn or broken.

Still another object of the invention is to provide a calk of the above-mentioned character that negatives the natural slipperiness of rubber when wet and that assures an effective grip under essentially all conditions.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the drawing forming a part of this specification and wherein like numerals are employed to designate like parts throughout the same:

Fig. 1 is a bottom plan view showing the rubber sole of a boot or the like equipped with calks embodying the invention;

Fig. 2 is a fragmentary, longitudinal, sectional view taken on the line 2 2 of Fig. 1 showing a. socket embodying a part of the calk assembly embedded in the sole of the shoe and illustrating the body of the calk itself screwed into the socket;

Fig. 3 is a View similar to Fig. 2 but illustrating the calk disengaged from the socket;

Fig. 4 is a longitudinal, sectional view through a moditied calk embodying the invention;

Fig. 5 is a transverse, sectional view taken on the line 5'5 of Fig. 4;

Fig. 6 is a longitudinal, sectional view through still another modified calk embodying the invention; and

Fig. 7 is a transverse, sectional view taken on the line 7-7 of Fig. 6.

In the drawing, wherein for the purpose of illustration is shown a preferred embodiment of the invention, the numeral 1% designates the sole of a boot or the like. The sole 1i conventionally consists of a relatively thin inner sole 12 and a relatively thick outer sole 14. Both the inner sole 12 and the outer sole 14 are here shown of rubber.

According to the present invention a plurality of calk assemblies 16 are embedded in the thick outer sole 14. Each assembly 16 comprises a socket 118 and a calk 20. The sockets 13 preferably extend through the full. width or thickness of the outer sole 14 so that the bottoms of atent 2,758,396 Fatented Aug. 14,, 19.56

the sockets bear against the inner sole- 1-2 and the outer edges or mouths of the sockets terminate flush with the under or outer surface of the outer sole 14. The calks 20 extend inwardly to the bottom of the socket 18 and they project therefrom. a suitable distance below the bottom of the sole 10. Any suitable or desired number of the calk assemblies can be mounted in the sole 1'0 and they can be arranged or distributed in any suitable manner over the area of the sole. Four calk assemblies 16 are here shown by way of illustration (Fig. 1) in the front portion of the sole and two calk assemblies are provided in the heel portion thereof. The calks 20 of the several assemblies 16 preferably project uniform distances below the sole so that each contacts the surface being traversed and contributes to the support of the wearer;

The sockets 1i and studs 20 can be made of any suitable material. Metal is perhaps the best material but various other materials such as plastic resins, for example, can be used if desired. To prevent rusting, the elements 18 and 2% can be suitably platedif made of steel or, alternatively and advantageously, they can be made from aluminum or magnesium alloys. If these elements are made of plastic, they preferably are suitably reinforced and strengthened as by a glass mat or cloth filler or the like.

The sockets 18 preferably are inserted into the molded rubber compound of the outer sole 14 prior to vulcanization. A simple method of doing this is simply to press the sockets into the relatively soft-sole material before the latter is introduced into the mold for vulcanization a sufiicient distance to dispose the open mouths of the sockets flush or substantially flush with the outer surface of the sole. Of course, the closed bottoms of the sockets prevent the rubber material from entering the sockets from below. A thin film of rubber may flow over and close the open ends of the sockets due to pressure in the mold, but this film can be easily punched out after vulcanization to permit insertion of the calks 20. If the sockets are made of metal, the outer surfaces thereof preferably are treated with a suitable rubber-to-metal bonding agent to assure an essentially strong bond between the rubber material of the sole 14 and the metal bodies of the sockets. Also, the sockets 18 preferably are formed to provide a. mechanical interlocking connection between them and the rubber outer sole 14. In the particular form of the invention here shown by way of illustration, the sockets are provided with external, relatively coarse threads 22 which mechanically interlock with the rubber in an obvious manner.

The calks 20 are in the form of elongate bodies having external threads 22 which engage internal threads 24 provided in the sockets 18. The threaded connections be,-

. tween the sockets 18 and the calks 211 permit the latter to be readiiy inserted into or removed from the sockets and thus permits the calks to. be easily replaced when the. become worn or broken. A double. thread preferably is employed to facilitate insertion and removal of the calks 20. As suggested, the calks screw all of the way intoand seat on the bottoms of the sockets 13 so as to relieve the connecting threads 22 and 2. and. to provide solid support for the calks. The projecting outer ends of the calks 20 are formed, with central cupped depressions, or concave surfaces 26 which define essentially thin peripheral edges 28, and the latter, in combination with the concave cont figurations, provide a particularly effective gripping action. Under certain conditions where the edges 28 flatly engage a supporting surface, a suction effect is. produced by the concavities 26 which assists the calk in gripping the sur-. face. Under other conditionsv such as those encountered in wading a stream, for example, the cupped edges of the calks also provide. a. superior grip. or traction. When in contact with a stone surface the. comparatively thinv edges 2,8 produce a slight indentation due to the. weight imposed on them, thereby insuring a firm grip on the surface.

Also, slight irregularities in the surface engaged by the calks tend to enter the concavities 26 and to be entrapped thereby so as to assist in effective anchorage. In the case of a stone surface covered by a slimy aquatic growth, a condition frequently encountered in streams, the cupped edges 26 easily cut through the deposit and effect a firm grip on the surface of the stone. Surfaces such as clay or sand are easily penetrated by the calks which are thus able to secure an effective nonslip grip. It is desirable, for reasons set forth above, that the cupped edges 28 be essentially thin. However, the actual thickness thereof may be varied somewhat, depending upon the condition of employment. In the case of fishing waders and the like the edges 26 should be sufliciently thin to provide an effective cutting action, whereas, in the case of seamen's boots, for example, the edges 23 probably would be made relatively blunt to avoid scratching the deck surface.

Under certain conditions of use the gripping action of the calks can be enhanced if the peripheral edge portions 23 are dissected by radial slots or grooves as shown in Figs. 4-7. These slots 30 preferably extend to the bottom of the cup depressions 26 and they provide a plurality of individual segmental portions each of which yields and flexes in use independently of the others. Each segmental portion provides a spiingy talon or claw grip which possesses distinct advantages under circumstances where a quick gripping action is essential, as where the wearer jumps or steps quickly from one surface to another.

The effective gripping action of the calk can be still further enhanced under certain conditions by treating at least certain of the segmental portions defined by the slots 30 to modify the coefficient of friction afforded thereby. All of the segmental portions can be so treated, but under many circumstances only part of these portions need be treated. In fact certain advantages are obtained if some of these segmental portions are treated to modify their coefficient of friction while other segmental portions are left untreated. One way of treating the segmental portions as described above is to coat them with a plastic resin film. Any plastic resin suitable for this purpose can be used, typical examples of such resins being the polyvinyls, nylons, and polyethylenes. Polyvinyl resins are pre-eminently satisfactory in this connection. In the two forms of the invention illustrated in Figs. 4-7 the cup rim 28 of each calk 20 is dissected by equispaced radial slots 30. In the form of the invention shown in Figs. 4 and 5, alternate segmental portions only are coated with plastic resin films 32, and in the form of the invention shown in Figs. 6 and 7 three segmental sections at one side of the calk are covered with a plastic resin film 34 while the three segmental sections at the other side of the calk are untreated. By coating certain of the segmental portions of the ealks 20 with a film of plastic resin in the manner described, the sharp cutting edges of the calks are raised so that they do not engage or damage a smooth surface such as a floor or the like. Only the plastic resin surfaces engage the floor and they do not mar or otherwise damage the same. At the same time, the plastic resin material provides an eflicient nonskid action on a smooth surface such as a floor, for example. On the other hand, when the calk is used in more rugged surroundings, the relatively sharp edges of the uncoated segmental portions are available for use in the manner hereinabove described. Also, the provision of the plastic resin film 32 does not in any way impair the effective gripping action of the cupped undersurface 26.

Having thus described the invention, 1 claim:

1. A shoe calk having an inner end portion received and fixed within a shoe sole and having a cylindrical outer end portion projecting outwardly from the outer surface of the sole, said calk also having a concave outer end surface extending to the cylindrical outer surface thereof around the entire circumference of the calk and cooperating therewith to define a relatively sharp, downwardly directed peripheral edge, and the innermost portion of from the outer surface of the sole, said peripheral edge being dissected by radial slots and said slots defining a plurality of segments which are individually laterally flexible to provide discrete gripping elements.

2. A shoe calk comprising an elongate body having a cylindrical side surface and a concave end extending to said cylindrical side surface and defining an essentially thin, sharp, downwardly directed, annular peripheral edge portion, said peripheral edge portion being dissected by radial slots, and the individual segmental portions defined by said slots being individually flexible and providing discrete gripping elements, and means on the gripping elements at one side of said calk providing the mentioned gripping elements with a different coefficient of friction than the gripping elements at the opposite. side of the calk.

3. A shoe calk comprising an elongate body having a cylindrical side surface and a concave end extending to said cylindrical side surface and defining a sharp, downwardly directed, annular peripheral edge portion, said peripheral edge portion being dissected by radial slots, and the individual segmental portions defined by said slots being individually flexible and providing discrete gripping elements, and means on and bonded to alternate flexible gripping elements providing a different coefficient of friction therefor than the other of said flexible gripping ele ments.

4. A shoe calk comprising an elongate body having a side surface and a concave end extending to said side surface and cooperating therewith to define a sharp, down wardly directed, peripheral edge portion, said peripheral edge portion being dissected by radial slots and said slots defining a plurality of segments, the segments defined by said slots being individually laterally flexible and providing discrete gripping elements, and means associated with some but not all of said segments providing a different coefficient of friction therefor than is provided by the other of said segments.

5. A shoe calk having a side surface and a concave end extending to said side surface and co-operating therewith to define a relatively thin, downwardly directed, peripheral, gripping edge, the concave end of said calk being dissected by radial grooves and said grooves dividing said gripping edge portion into individual segmental sections each capable of flexing independently of the other, and surface films coating and bonded to some of said segmental sections, other of said sections being free of said surface films, said surface films providing the segmental sections to which they are bonded with a coeflicient of friction which is different than the coefficient of friction of the said uncoated sections.

6. A shoe calk comprising an elongate body having a side surface and a concave end extending to said side surface and co-operating therewith to define a sharp, downwardly directed, peripheral edge portion, said peripheral edge portion being dissected by radial slots and said slots defining segmental portions, the individual segmental portions defined by said slots being individually flexible and providing discrete gripping elements, and resinous films coating some of said gripping elements and other of said gripping elements being free of said coating, said resin providing said coated gripping elements with a different coeflicient of friction than said uncoated gripping elements.

References Cited in the file of this patent UNITED STATES PATENTS 167,239 Guilford Aug. 31, 1875 315,293 Ihrig Apr. 7, 1885 366,158 Dow July 5, 1887 697,135 Dearing Apr. 8, 1902 1,292,681 Beck Jan. 28, 1919 2,222,650 Brady Nov. 26, 1940 2,330,458 Tubbs Sept. 28, 1943 FOREIGN PATENTS 7045/12. Great Britain Feb. 13, 1913 

